pkgmaker: Package development utilities

This package provides some low-level utilities to use for package
development. It currently provides managers for multiple package specific
options and registries, vignette, unit test and bibtex related utilities.
It serves as a base package for packages like NMF, RcppOctave, doRNG, and
as an incubator package for other general purposes utilities, that will
eventually be packaged separately.
It is still under heavy development and changes in the interface(s) are
more than likely to happen.